I use such a setup on my Solids instrument (std. equipment on the old
Chemagnetics systems). It's very useful to monitor forward vs. reflected
power to optimize probe tuning (which, under high-power conditions, can
change simply by adjusting the pulse-delay/duty-cycle). When testing a new
pulse-sequence, it's also nice to see the Rf coming out the way it should
(as you mentioned). I _don't_ have a digital-storage scope, and have
to watch the pulses "on the fly"...it serves my needs, however. I haven't
desired this capability on my liquids instruments, simply because of
the less-demanding tolerances w/ low-power Rf.
The directional-coupler (Bird) is in-line w/ both Rf channels all the time,
so the 90s, phases, ...etc. are calibrated w/ the coupler in-place; therefore,
having it there doesn't add any experimental difficulties.
I would say that it might not be that useful for extremely complex liquid-
state pulse sequences. I check-out those experiments by looking at the data
(those spins are really good at telling me if my sequence is running right 8-).
Cheers,
Rich Shoemaker
-- Richard Shoemaker, Ph.D. Phone--(402) 472-6255 Instrumentation Director, Chemistry FAX---- -6964 Research Associate Professor, Chemistry University of Nebraska-Lincoln URL: http://wwitch.unl.edu/nmrlab.html